This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A newly described signaling pathway in Escherichia coli, the QseBC two-component signal transduction (TCST) system, has been proposed to be involved in both interspecies cell-cell communication and host-pathogen interaction. A homolog to the QseBC system has been identified in NTHi. This system, which I have designated QshABC, has a novel operon organization that includes a gene, qshA, that encodes for a small periplasmic protein. A qshBC mutant exhibits severely attenuated biofilm formation and/or persistence in the chinchilla model for otitis media while it is unaffected in its ability to form a biofilm in vitro. Based on these observations, I propose to further characterize the QshABC system in NTHi to assist in the exploration of its role in pathogenesis. Successful completion of the proposed work would be a crucial step in the characterization of this system and will lead to a better understanding of the signal transduction pathways that are required for the virulence of NTHi.